Reticle transfer system and method

ABSTRACT

A method comprises transporting semiconductor devices between a global system and a local system, wherein an input terminal of the local system is connected to the global system, and wherein the global system comprises a plurality of stockers and a global transportation system connected to the stockers and the local system comprises a first service area, an internal buffer, a second service area and a plurality of lithography apparatuses and transporting a semiconductor device from the first service area to a lithography apparatus in the second service area.

This application is a divisional of U.S. patent application Ser. No.15/069,479, entitled “Reticle Transfer System and Method,” filed on Mar.14, 2016, which is a divisional of U.S. patent application Ser. No.13/648,034, entitled “Reticle Transfer System and Method,” filed on Oct.9, 2012, now U.S. Pat. No. 9,287,150, which application is incorporatedherein by reference.

BACKGROUND

The semiconductor industry has experienced rapid growth due toimprovements in the integration density of a variety of electroniccomponents (e.g., transistors, diodes, resistors, capacitors, etc.). Forthe most part, this improvement in integration density has come fromshrinking the semiconductor process node (e.g., shrink the process nodetowards the sub-20 nm node). As semiconductor devices are scaled down,new techniques are needed to maintain the electronic components'performance from one generation to the next. Device complexity isincreasing as manufacturers design smaller feature sizes and morefunctionality into integrated circuits. Such complex devices may resultin more lithography steps.

As semiconductor technologies evolve, advanced lithography techniqueshave been widely used in today's integrated circuit fabricationprocesses. Photolithographic techniques involves forming a photoresistlayer over a substrate, exposing portions of the photoresist material toa pattern of light in accordance with a desired pattern, developing thephotoresist material to remove portions of the photoresist material toexpose portions of the underlying material. A suitable etching processsuch as dry etching, wet etching and/or the like may then be performedon the substrate. As a result, the exposed underlying material may beremoved in accordance with the desired pattern.

The exposure step of the lithography process may involve a variety ofreticles (a.k.a. photo masks). Each reticle is a quartz plate havingtransparent and opaque regions. The transparent and opaque regionsreplicate a pattern representing an integrated circuit component on thesurface of a wafer. The lithography process of the integrated circuitmay comprise multiple photolithography process steps due to thecomplexity of the manufacturing process. Each lithography step mayemploy a reticle through which the pattern of a component of anintegrated circuit is generated.

An integrated circuit fab may comprise a variety of lithographyapparatuses such as steppers, immersion scanners and the like. Inaddition, the fab may have a plurality of stockers for storing wafersand reticles. The factory is automated by using automatic guidedvehicles to transport wafers and reticles and using robots to loadwafers and reticles into lithography apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a layout of an integrated circuit fab in accordancewith an embodiment;

FIG. 2 illustrates a simplified layout of the local system of anintegrated circuit fab in accordance with an embodiment;

FIG. 3A illustrates a layout of the local system prior to moving theinternal buffer in accordance with an embodiment;

FIG. 3B illustrates a layout of the local system after moving theinternal buffer in accordance with an embodiment; and

FIG. 4 illustrates a layout of the local system in accordance withanother embodiment.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the variousembodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently embodiments are discussed indetail below. It should be appreciated, however, that the presentdisclosure provides many applicable inventive concepts that can beembodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the disclosure, and do not limit the scope of the disclosure.

The present disclosure will be described with respect to embodiments ina specific context, namely a reticle transportation system. Theembodiments of the disclosure may also be applied, however, to a varietyof transportation systems of an integrated circuit fab. For example, themethod described below may be applicable to a wafer transportationsystem in the fab. More particularly, the method may be applied to awafer transfer management system including moving a front openingunified pod (FOUP) from a location to another location in the fab.Hereinafter, various embodiments will be explained in detail withreference to the accompanying drawings.

FIG. 1 illustrates a layout of an integrated circuit fab in accordancewith an embodiment. For simplicity, only relevant portions of anintegrated circuit fab are included in the layout 100. One personskilled in the art will recognize that FIG. 1 is a simplified diagramillustrating the operation of transporting wafers and reticles betweendifferent locations according to an embodiment. This diagram is merelyan example, which should not unduly limit the scope of the claims. Oneof ordinary skill in the art would recognize many variations,alternatives, and modifications.

In accordance with an embodiment, an integrated circuit fab may comprisea main aisle and a plurality of bays connected to the main aisle. Aplurality of stockers may be placed at either side of the main aisle. Anoverhead transportation system over the main aisle may transportreticles and wafers from one stocker to another stocker. Alternatively,a rail system at ground level may be used to fulfill the sametransportation function.

Each bay may comprise a variety of lithography apparatuses, which areemployed to fulfill different functions of a lithography process. Thetransportation through the main aisle is commonly referred to asinter-bay transportation. On the other hand, the transportation within asingle bay is commonly referred to as intra-bay transportation.

According to different transportation characteristics, the layout 100may be divided into two regions, namely a global system 110 and a localsystem 120. As shown in FIG. 1, the global system 110 and the localsystem 120 are demarcated by a dashed line 102. In accordance with anembodiment, the global system 110 may comprise a main aisle, a railtransportation system (a.k.a. a global transportation system) and aplurality of stockers used for storing wafers and reticles. The stockersmay be a clean environment closet full of inert gas. A reticle and/orwafer may be stored in the stocker when the reticle and/or wafer are notprocessed. On the other hand, the reticle and/or the wafer may beretrieved from the stocker if the reticle and/or wafer will be used by alithography apparatus.

As shown in FIG. 1, the stockers of the global system 110 are coupled toeach other through the global transportation system. The globaltransportation system may include a variety of overhead rails andcarriers (a.k.a. automatic guided vehicles). A wafer or a reticle may beloaded into a carrier from a stocker by a robot. Furthermore, the waferor the reticle may be transported to another stocker in the globalsystem 110 or an input terminal of the local system 120.

It should be noted that the container carrying reticles may be differentfrom the container carrying wafers. In accordance with an embodiment,the reticle container may be a reticle storage pod (RSP). On the otherhand, the wafer container may be a front opening unified pod (FOUP).

The local system 120 is coupled to the global system 110 through atleast one overhead rail. There may be a buffer located at the boundarybetween the local system 120 and the global system 110. A wafer or areticle may be temporarily stored at the buffer when the overhead railcoupled to the buffer is jammed or the destination apparatus of thelocal system 120 is not available.

The local system 120 may comprise a variety of lithography apparatusessuch as immersion scanners, stepper and/or the like. All lithographyapparatuses are coupled to each other through a local transportationsystem. The local transportation system may include a variety ofoverhead rails and carriers. A wafer, a reticle, a group of waferscarried by a pod such as FOUP may be loaded into/from a scannerfrom/into a carrier by a robot such as a 3-axis reticle handling arm.Furthermore, the wafer or the reticle may be transported to anotherscanner or to the global system through the overhead rail of the localtransportation system. The detailed layout of the local system 120 willbe described below with respect to FIG. 2.

One advantageous feature of dividing a fab layout into a global systemand a local system is that the local system may be of an independenttransportation system. As such, the system shown in FIG. 1 can avoidsome common issues of the close-loop transportation system of a fab. Forexample, in order to short the response time, the close-looptransportation may employ many carriers cycling in loop to keep a shortresponse time and need a dedicated loop for each scanner. Furthermore,the system may need a variety of rails between stockers and scanners tosolve the traffic jam issue. By employing the layout shown in FIG. 1,the traffic between the global system and the local system has beenreduced. As such, the traffic jam between the global system and thelocal system may be alleviated. Therefore, few carriers are needed sothat the production cycle time and tool efficiency may be improved.

FIG. 2 illustrates a simplified layout of the local system of anintegrated circuit fab in accordance with an embodiment. The localsystem 120 may comprise a plurality of lithography apparatuses such asscanners. The scanners reside along two sides of a local aisle. As shownin FIG. 2, scanners A1, A2, A3, A4, A5, A6 and A7 reside at a first sideof the local aisle. Scanners B1, B2, B3, B4, B5, B6 and B7 reside at asecond side of the local aisle. There may be a transportation systemlocated over the local aisle. The transportation system may include tworails, namely a first rail 222 and a second rail 224. As shown in FIG.2, the first rail 222 provides reticle/wafer transportation for thescanners A1, A2, A3, A4, A5, A6 and A7. Likewise, the second rail 224provides reticle/wafer transportation for the scanners B1, B2, B3, B4,B5, B6 and B7.

It should be noted that depending on different applications andconstraints, the rails may be built at ground level. Alternatively, anoverhead rail system may be employed to save ground level space. Itshould further be noted while the system and method described below maybe applicable to both reticles and wafers, a reticle transfer system isused as an example to illustrate the innovative aspects of variousembodiments.

Each scanner such as A1 may include a scanner apparatus 252 and areticle port 254 embedded in the scanner apparatus 252. In particular,the reticle port 254 may be a loading platform located in the scannerand adjacent to a process chamber of the scanner apparatus 252. Aconveyor 258 couples the scanner apparatus 252 with the localtransportation system. More particularly, as shown in FIG. 2, when areticle is transported from the local transportation system to thescanner apparatus 252 through the conveyor 258, a robot 256 loads thereticle into the reticle port 254. On the other hand, when a reticle isnot processed, the reticle is loaded into the reticle port 254 from thescanner apparatus 252. The robot 256 further loads the reticle into theconveyor 258 from the reticle port 254. In accordance with anembodiment, the robot 256 may be a 3-axis reticle handling arm. Itshould be noted that scanners can be employed to store reticles. In someembodiments, a scanner can accommodate 6 to 8 reticles.

There may be two reticle buffers 212 and 214 in the local system 120.The reticle buffers 212 and 214 are coupled to both the first rail 222and the second rail 224. As shown in FIG. 2, the first reticle buffer212 and the second reticle buffer 214 are on opposite sides of the localaisle. One of the reticle buffers (e.g., reticle buffer 212) mayfunction as a buffer between the global system 110 and the local system120. The reticle buffer 212 may be alternatively referred to as a firstbuffer. The region where the global system 110 is located may bealternatively referred to as a first region. The region where the localsystem 120 is located may be alternatively referred to as a secondregion.

In addition, the reticle buffers 212 and 214 may be used to store emptypods including FOUP, RSP and/or the like. More particularly, a pod suchas RSP is a closed container. The closed container may carry onereticle. When a reticle is loaded into its corresponding scannerapparatus, the empty pod may be transported to a stocker according to aconventional factory automation mechanism. Such a long distance transfermay cause a traffic jam, which in turn delays the response time ofloading/unloading reticles. Storing empty pods in the reticle buffers212 and 214 may reduce long distance transportation. As a result, thetraffic jam issue of the system can be alleviated.

It should be noted that storing empty pods in the reticle buffers 212and 214 is merely an example, which should not unduly limit the scope ofthe claims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. For example, in a fabhaving an overhead rail transportation system in the local system, theempty pods may be stored at an overhead storage area adjacent to theoverhead rail.

In consideration with the location of lithography apparatuses, the localsystem 120 may be divided into two service areas. The first service area202 extends from the first reticle buffer 212 to the conveyor of thescanner A5. The second service area 204 extends from the conveyor of thescanner A5 to the second reticle buffer 214. There may be two carriers(a.k.a vehicles) 216 and 217 dedicated to the first service area 202.Likewise, carriers 218 and 219 are employed to transport reticle withinthe second service area 204. It should be noted the definition of thefirst service area and the second service area is not fixed. Theterritory of each service area may change by adjusting an internalbuffer. The detailed operation of the internal buffer will be describedbelow.

It should be recognized that while FIG. 2 illustrates the local system120 with fourteen scanners and two service areas, the local system 120could accommodate any number of scanners and service areas. The numberof scanners and service areas illustrated herein is limited solely forthe purpose of clearly illustrating the inventive aspects of the variousembodiments. The present disclosure is not limited to any specificnumber of scanners and service areas.

The local system 120 may further comprise an internal buffer 206 locatedbetween the first reticle buffer 212 and the second reticle buffer 214.More particularly, the internal buffer 206 is a movable component. Thedefault position of the internal buffer 206 is at the boundary of thefirst service area 202 and the second service area 204. In considerationwith the need of transporting reticles efficiently, the location of theinternal buffer 206 may change accordingly. The detailed operation ofthe internal buffer 206 will be described below with respect to FIG. 3and FIG. 4.

One advantageous feature of having the local system layout shown in FIG.2 is that the adjustable internal buffer helps to improve the scannerproductivity so that the total cost of manufacturing integrated circuitscan be reduced.

FIG. 3A illustrates a layout of the local system prior to moving theinternal buffer in accordance with an embodiment. As indicated by adashed curve 302, a reticle will be transported from the scanner A1 tothe scanner A6. A system controller (not shown) may check the activitiesof both service areas before adjusting the location of the internalbuffer 206. In accordance with an embodiment, the second service area isidle. In other words, there is no reticle transportation in the secondservice area. The system controller may move the internal buffer 206from its default point scanner A5's conveyer to a location beyond thescanner A6 so that the carrier 216 may deliver the reticle to thescanner A5 directly.

FIG. 3B illustrates a layout of the local system after moving theinternal buffer in accordance with an embodiment. The internal buffer206 has been moved to the location adjacent to the conveyor of thescanner A7. As a result, the carrier 216 may deliver the reticle to theconveyor of the scanner A6 directly. One advantageous feature of havingadjustable internal buffer is that the internal buffer stage may bebypassed so that the time of moving a reticle may be reduced.

FIG. 4 illustrates a layout of the local system in accordance withanother embodiment. As indicated by dashed curves 402 and 404, a firstreticle will be transported from the scanner A1 to the scanner A6. Atthe same time, a second reticle will be transported from the scanner A7to the scanner A6. As a result, there is conflict between these tworeticle moving events. In consideration with this conflict, the systemcontroller may not adjust the location of the internal buffer 206. Thesecond reticle will be transported to the scanner A6 by the carrier 218.The first reticle will be transported to the internal buffer 206 by thecarrier 216. After the carrier 218 is available, the first reticle isloaded into the carrier 218 and transported to the scanner A6subsequently.

Although embodiments of the present disclosure and its advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the present disclosure, processes, apparatuses,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed, that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein may be utilized according to the presentdisclosure. Accordingly, the appended claims are intended to includewithin their scope such processes, apparatuses, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. A method comprising: transporting wafers andreticles between a global system and a local system, wherein an inputterminal of the local system is connected to the global system, andwherein the local system comprises: a first buffer at a boundary betweenthe global system and the local system; a second buffer at a defaultposition of the local system, wherein the default position is a boundarybetween a first service area and a second service area, wherein thefirst service area comprises at least one carrier, wherein the secondbuffer and the at least one carrier are independently moveable; and athird buffer at an end of the local system, wherein the first servicearea is from the first buffer to the second buffer and the secondservice area is from the second buffer to the third buffer; transportinga reticle from a first scanner in the first service area to a secondscanner in the second service area; adjusting the boundary between thefirst service area and the second service area by moving the secondbuffer, wherein the second scanner is in the first service area as aresult of performing the step of adjusting the boundary between thefirst service area and the second service area; and transporting thereticle to the second scanner.
 2. The method of claim 1, wherein: theglobal system includes a rail transportation system, a plurality ofstockers and a main aisle.
 3. The method of claim 2, further comprising:storing a wafer at a stocker when the wafer is out of a processingapparatus; and retrieving the wafer from the stocker before sending thewafer into the processing apparatus.
 4. The method of claim 1, wherein:the local system comprises a plurality of lithography apparatuses, andwherein the plurality of lithography apparatuses are coupled to eachother through a local transportation system comprising a plurality ofoverhead rails and carriers.
 5. The method of claim 4, furthercomprising: moving a reticle between a conveyor and a lithographyapparatus using a robot, wherein the conveyor is between the localsystem and the plurality of lithography apparatuses, and wherein therobot is coupled between the conveyor and a reticle port embedded in thelithography apparatus.
 6. The method of claim 1, further comprising:loading a wafer into a carrier using a robot.
 7. The method of claim 1,further comprising: storing an empty pod in the first buffer, whereinthe empty pod is a closed container for carrying reticles.
 8. The methodof claim 1, further comprising: storing an empty pod in an overheadregion, wherein the empty pod is a closed container for carryingreticles.
 9. The method of claim 1, wherein the local system comprises:an aisle, wherein a first terminal of the aisle is connected to thefirst buffer; a first rail coupled between the first buffer and a firstgroup of lithography apparatuses; a second rail coupled between thefirst buffer and a second group of lithography apparatuses, wherein thefirst group of lithography apparatuses and the second group oflithography apparatuses are on opposite sides of the aisle; the thirdbuffer connected to a second terminal of the aisle; and the secondbuffer located between the first buffer and the second buffer, whereinthe second buffer is adjustable.
 10. The method of claim 9, furthercomprising: placing a first carrier on the first rail, wherein the firstcarrier is located in the first service area; placing a second carrieron the first rail, wherein the second carrier is located in the secondservice area; placing a third carrier on the second rail, wherein thethird carrier is located in the first service area; and placing a fourthcarrier on the second rail, wherein the fourth carrier is located in thesecond service area.
 11. A method comprising: transporting semiconductordevices between a global system and a local system, wherein an inputterminal of the local system is connected to the global system, andwherein: the global system comprises a plurality of stockers and aglobal transportation system connected to the stockers; and the localsystem comprises at least one carrier, a first service area, an internalbuffer independently moveable from the at least one carrier, a secondservice area and a plurality of lithography apparatuses; andtransporting a first semiconductor device from the first service area toa lithography apparatus in the second service area.
 12. The method ofclaim 11, wherein the local system comprises: a first buffer located ata boundary between the global system and the local system; a first railcoupled between the first buffer and a first group of lithographyapparatuses; a second rail coupled between the first buffer and a secondgroup of lithography apparatuses; a second buffer at an end of the localsystem; and an internal buffer located between the first buffer and thesecond buffer, wherein the internal buffer is adjustable.
 13. The methodof claim 12, further comprising: adjusting a boundary between the firstservice area and the second service area by moving the internal buffer,wherein the lithography apparatus is in the first service area as aresult of performing the step of adjusting the boundary between thefirst service area and the second service area.
 14. The method of claim11, wherein the global system includes: a plurality of rail loopsconnected between the plurality of stockers and the local system, andwherein the plurality of rail loops forms an overhead transportationsystem over a main aisle of the global transportation system; and aplurality of bays connected to the main aisle, wherein each baycomprises a plurality of lithography apparatuses.
 15. The method ofclaim 14, further comprising: transporting the semiconductor devicesthrough the main aisle using an inter-bay transportation apparatus; andtransporting the semiconductor devices within a single bay through anintra-bay transportation apparatus.
 16. A method comprising:transporting semiconductor devices between a first system and a secondsystem, the second system being a local system, the second systemcomprising a first buffer at a boundary between the first system and thesecond system, a second buffer at an end of the local system, a firstservice area, a second service area and a third buffer at the boundarybetween the first service area and the second service area; transportinga semiconductor device from a first scanner in the first service area toa second scanner in the second service area by loading the semiconductordevice from the first scanner into a carrier; determining whether aconflicting reticle transfer event occurs in the second service area;after the step of determining whether a conflicting reticle transferevent occurs in the second service area, adjusting a boundary betweenthe first service area and the second service area by moving the thirdbuffer, wherein the second scanner is in the first service area as aresult of performing the step of adjusting the boundary between thefirst service area and the second service area; and transporting thesemiconductor device to the second scanner by the carrier.
 17. Themethod of claim 16, wherein the first system is a global systemcomprising: a global transportation system including a plurality ofoverhead rails and carriers.
 18. The method of claim 17, furthercomprising: loading the semiconductor device from a first stocker of aglobal system by a robot; and transporting the semiconductor device to asecond stocker of the global system by a carrier of the global system.19. The method of claim 18, wherein the robot comprises a 3-axis reticlehandling arm.
 20. The method of claim 18, wherein the carrier of theglobal system comprises a reticle storage pod.